- 标题
- 摘要
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- 实验方案
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Estimating the Individual Spectroscopic Properties of Three Unique Eu <sup>III</sup> Sites in a Coordination Polymer
摘要： We isolated a coordination polymer with the formula [Eu3(3,5-dcba)9(H2O)(dmf)3]·2dmf, with three unique EuIII coordination sites in the asymmetric unit, with the EuIII ions bridged by 3,5-dichlorobenzoato (3,5-dcba) ligands. The coordination polymer crystallized in the triclinic space group P1? with unit cell dimensions a = 12.4899(15), b = 16.326(2), and c = 25.059(3) ?, α = 84.271(3)°, β = 84.832(3)°, and γ = 68.585(3)° and V = 4725.2(10) ?3. The characteristic 5D0 → 7FJ (J = 0?4) EuIII transitions were observed upon ligand-centered excitation. Emission lifetimes of 0.825 ± 0.085 and 1.586 ± 0.057 ms were observed and were attributed to the sites with coordination of water or dimethylformamide (dmf) molecules to each ion, respectively. Through a combination of spectroscopy and calculations, we determined the photophysical properties of each unique EuIII site. Energy-transfer rates ligand → EuIII were determined for each unique site using the overlapped polyhedra method. The rates depend on the coordinated water molecules and the different donor?acceptor distances. The two sites without coordinated water molecules and shortest donor?acceptor distance display the fastest energy-transfer rate ligand → EuIII, whereas the site with coordinated water molecules and longest donor?acceptor distance displays the slowest energy-transfer rate. Donor?acceptor distances were estimated computationally and were confirmed by calculating the frontier orbitals in the asymmetric units of the polymer using density functional theory.
关键词： coordination polymer,photophysical properties,energy-transfer rates,density functional theory,EuIII
更新于2025-09-09 09:28:46
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Designing Long-Range Charge Delocalization from First Principles
摘要： Efficient electronic communication over long distances is a desirable property of molecular wires. Charge delocalization in mixed-valence (MV) compounds where two redox centers are linked by a molecular bridge is a particularly well-controlled instance of such electronic communication, thus lending itself to comparisons between theory and experiment. We study how to achieve and control long-range charge delocalization in cationic organic MV systems by means of Kohn–Sham density functional theory (DFT), and show that a captodative substitution approach recently suggested for molecular conductance (T. Stuyver et al., J. Phys. Chem. C 122, 3194 (2018)) greatly enhances charge delocalization in para-phenylene-based wires. To ensure the adequacy of our DFT methods, we validate different protocols for organic MV systems of different lengths. The BLYP35 hybrid functional combined with a polarizable continuum model, established by Renz and Kaupp, is indeed capable of correctly describing experimentally observed length-dependent charge delocalization, in contrast to the long-range corrected functionals ω-B97X-D and ω-PBE. We also discuss the implications of these results for a first-principles description of the transition between coherent tunneling and incoherent hopping regimes in molecular conductance.
关键词： Charge Delocalization,Molecular Wires,Mixed-Valence Compounds,Quantum Electronic Structure,Density Functional Theory
更新于2025-09-09 09:28:46
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Revealing the Spectrum of Unknown Layered Materials with Super-Human Predictive Abilities
摘要： We discover the chemical composition of over 1000 materials that are likely to exhibit layered and two-dimensional phases but have yet to be synthesized. This includes two materials our calculations indicate can exist in distinct structures with different band gaps, expanding the short list of two-dimensional phase change materials. While databases of over 1000 layered materials have been reported, we provide the first full database of materials that are likely layered but yet to be synthesized, providing a roadmap for the synthesis community. We accomplish this by combining physics with machine learning on experimentally obtained data and verify a subset of candidates using density functional theory. We find our model performs five times better than practitioners in the field at identifying layered materials and is comparable or better than professional solid-state chemists. Finally, we find that semi-supervised learning can offer benefits for materials design where labels for some of the materials are unknown.
关键词： two-dimensional materials,machine learning,materials discovery,density functional theory,layered materials
更新于2025-09-09 09:28:46
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Optical spatial differentiator for a synthetic three-dimensional optical field
摘要： We propose a grating-based spatial differentiator to process a synthetic three-dimensional optical field, where several conventional two-dimensional optical images are stacked at multiple wavelengths. The device simultaneously enables both spatial differentiation and demultiplexing during light diffraction. We show the spatial differentiation resulting from coupling and interference of spatial modes and derive the theoretical condition for spatial differentiation based on spatial coupled-mode theory. We numerically investigate field transformation during diffraction and demonstrate spatial differentiation with image processing of edge detection for a synthetic three-dimensional optical field, where four images are stored at different wavelengths.
关键词： demultiplexing,coupled-mode theory,grating-based,spatial differentiation,optical spatial differentiator,synthetic three-dimensional optical field
更新于2025-09-09 09:28:46
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FIRST PRINCIPLES STUDY OF STRUCTURAL, ELECTRONIC AND OPTICAL PROPERTIES OF HALF-HEUSLER ALLOYS LIMGN, NaMGN AND KMGN
摘要： In this study, we performed our calculations using the full-potential linearized-augmented plane wave (FP-LAPW) method as implemented in the WIEN2k code based on DFT. The generalized gradient functional with the Wu-Cohen (WC) parameterization was used to evaluate the structural, electronic, optical and thermoelectric properties of the materials under this study. We have calculated the structural parameters and our obtained results are in good agreement with available experimental and previous theory calculations. The density of states and band structure figures have been calculated and analyzed. The optical properties that covered by dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity and energy-loss function have been calculated and analyzed in a range energy from 0eV to 30eV.
关键词： generalized gradient functional,dielectric function,reflectivity,absorption,half-Heusler,Density functional theory
更新于2025-09-09 09:28:46
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The Nature of the Oxygen Vacancy in Amorphous Oxide Semiconductors: Shallow Versus Deep
摘要： Using first-principles calculation, we investigate the nature of oxygen vacancy (VO), namely shallow versus deep, in the amorphous oxide semiconductor InGaZnO4 (a-IGZO), which has not been fully clarified despite its technological importance. Oxygen-deficient amorphous models are generated through the hybrid functional molecular dynamics (MD) simulations that allow for finding stable VO configurations while minimizing computational approximations. From eight independent models, we consistently find that VO serves as the shallow donor, increasing the Fermi level above the conduction band minimum. For comparison purpose, we also generate deep VO models by charging the system during MD simulations. It is found that deep VO is higher in the formation energy than shallow VO, confirming that shallow VO is the preferred type of oxygen vacancies in a-IGZO.
关键词： hybrid functional,computational physics,InGaZnO4,oxygen vacancy,density functional theory
更新于2025-09-09 09:28:46
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Resource theory of quantum non-Gaussianity and Wigner negativity
摘要： We develop a resource theory for continuous-variable systems grounded on operations routinely available within current quantum technologies. In particular, the set of free operations is convex and includes quadratic transformations and conditional coarse-grained measurements. The present theory lends itself to quantify both quantum non-Gaussianity and Wigner negativity as resources, depending on the choice of the free-state set—i.e., the convex hull of Gaussian states or the states with positive Wigner function, respectively. After showing that the theory admits no maximally resourceful state, we define a computable resource monotone—the Wigner logarithmic negativity. We use the latter to assess the resource content of experimentally relevant states—e.g., photon-added, photon-subtracted, cubic-phase, and cat states—and to find optimal working points of some resource concentration protocols. We envisage applications of this framework to subuniversal and universal quantum information processing over continuous variables.
关键词： Wigner negativity,quantum information processing,quantum non-Gaussianity,continuous-variable systems,resource theory
更新于2025-09-09 09:28:46
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Probability theory in conditional-averaging ghost imaging with thermal light
摘要： In ghost imaging with thermal light (GITL), the bucket signals are analog signals playing the role of weights in the algorithms of image reconstruction. However, diverse bucket signals seemed to be completely ignored in conditional-averaging GITL, which was recently proposed by two groups [Appl. Phys. Lett. 100, 131114 (2012); Chin. Phys. Lett. 29, 074216 (2012)]. Even so, positive and negative ghost images were obtained by averaging just partial reference signals. To understand this effect, one needs to determine the statistical relation between random bucket signals and reference signals. Here, we apply probability theory to GITL by regarding thermal light intensities as stochastic variables, and then deduce the joint probability density function between the bucket and reference signals. Positive and negative images are formed in ensemble averaging of the product of the reference signal and two logic quantities of the bucket signals. The visibility and contrast-to-noise ratio of these images in conditional-averaging GITL are analyzed in detail in both theory and experiment. As for applications, we perform an experiment of remote conditional-averaging GITL and verify that the image quality is maintained when the bucket signals are extremely attenuated. Our method can be applied to any ghost imaging scenarios in which the specific statistics of the optical source is given.
关键词： ghost imaging,visibility,conditional-averaging,probability theory,thermal light,contrast-to-noise ratio
更新于2025-09-09 09:28:46
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surface alloy
摘要： We have investigated the atomic and electronic structure of the (√3×√3)R30? SnAu2/Au(111) surface alloy. Low-energy electron diffraction and scanning tunneling microscopy measurements show that the native herringbone reconstruction of bare Au(111) surface remains intact after formation of a long-range ordered (√3×√3)R30? SnAu2/Au(111) surface alloy. Angle-resolved photoemission and two-photon photoemission spectroscopy techniques reveal Rashba-type spin-split bands in the occupied valence band with comparable momentum space splitting as observed for the Au(111) surface state, but with a hole-like parabolic dispersion. Our experimental findings are compared with density functional theory (DFT) calculation that fully support our experimental findings. Taking advantage of the good agreement between our DFT calculations and the experimental results, we are able to extract that the occupied Sn-Au hybrid band is of (s, d )-orbital character, while the unoccupied Sn-Au hybrid bands are of (p, d )-orbital character. Hence we can conclude that the Rashba-type spin splitting of the hole-like Sn-Au hybrid surface state is caused by the significant mixing of Au d with Sn s states in conjunction with the strong atomic spin-orbit coupling of Au, i.e., of the substrate.
关键词： angle-resolved photoemission spectroscopy,density functional theory,SnAu2/Au(111) surface alloy,Rashba-type spin splitting,two-photon photoemission spectroscopy
更新于2025-09-09 09:28:46
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with pentagonal structure
摘要： Structure-property relationships have always been guiding principles for materials discovery. Here we explore the relationships to discover two-dimensional (2D) materials with the goal of identifying 2D magnetic semiconductors for spintronics applications. In particular, we report a density functional theory + U study of single-layer antiferromagnetic (AFM) semiconductor CoS2 with the pentagonal structure forming the so-called Cairo tessellation. We ?nd that this single-layer magnet exhibits an indirect band gap of 1.06 eV with electron and hole effective masses of 0.52 and 1.93 m0, respectively, which may lead to relatively high electron mobility. The hybrid density functional theory calculations correct the band gap to 2.24 eV. We also compute the magnetocrystalline anisotropy energy (MAE), showing that the easy axis of the AFM ordering is along the b axis with a sizable MAE of 153 μeV per Co ion. We further calculate the magnon frequencies at different spin-spiral vectors, based on which we estimate the N′eel temperatures to be 20.4 and 13.3 K using the mean ?eld and random phase approximations, respectively. We then apply biaxial strains to tune the band gap of single-layer pentagonal CoS2. We ?nd that the energy difference between the ferromagnetic and AFM structures strongly depends on the biaxial strain, but the ground state remains the AFM ordering. Although the low critical temperature prohibits the magnetic applications of single-layer pentagonal CoS2 at room temperature, the excellent electrical properties may ?nd single-layer semiconductor applications in optoelectronic nanodevices.
关键词： two-dimensional materials,magnon frequencies,N′eel temperature,biaxial strain,Cairo tessellation,antiferromagnetic semiconductor,density functional theory,band gap,magnetocrystalline anisotropy energy,pentagonal structure,spintronics
更新于2025-09-09 09:28:46